Britain's statistics watchdog has rapped the Treasury over the knuckles for a chart which gave voters a "false impression" about the scale of Government investment in infrastructure, including flood defences.

The graph was included in the National Infrastructure Plan published alongside Chancellor George Osborne's Autumn Statement last December, and appeared to show that spending was spread broadly across a range of priorities from energy and transport to floods, communications and intellectual property.

But UK Statistics Authority chairman Sir Andrew Dilnot said the way the information was presented "could leave readers with a false impression of the relative size of investment between sectors".

It is the latest in a string of cases in which the UK Statistics Authority has taken the Government to task over its use of figures. In 2012, the watchdog corrected David Cameron over a claim that NHS spending had risen in real terms, while last year it said the Prime Minister was wrong to say the Government was paying down Britain's debts.

The Treasury graph displayed the level of Government investment in various types of major infrastructure projects on a bar chart with a "logarithmic" scale, where the gaps between £1 million, £10 million, £100 million, £1 billion, £10 billion and £100 billion were each represented by increments of the same size.

The chart clearly showed that transport and energy projects had more money spent on them than other priorities, but the logarithmic scale meant that the smallest bars - for intellectual property, worth £855 million, waste (£2.3 billion) and flood defences (£4 billion) - were still more than half the size of the largest, for energy at £218 billion.

Sir Andrew produced an alternative chart with a standard scale, on which the bar for flood defences was dwarfed by a bar for energy more than 50 times its size.

In a letter to Labour Treasury spokesman Chris Leslie, who raised concerns about the graph, Sir Andrew said: "HM Treasury told us that the scale was chosen to create a legible representation while recognising the disparities in the scale of investment between sectors.

"While I note that the use of a logarithmic scale is clearly indicated in the text of the report, and the figures underlying the chart are presented in a separate table, my view is that the chart could leave readers with a false impression of the relative size of investment between sectors."

Mr Leslie said: "Time and again, ministers are being warned not to mislead the public with false claims, dodgy statistics and biased graphs.

"Now George Osborne and the Treasury have been told off for misleading people about the Government's investment in infrastructure. For example, their chart made it look like investment in flood defences was roughly the same as in other areas, when in fact it was a tiny fraction.

"This Government has a track record of trying to pull the wool over people's eyes. David Cameron has now been rebuked several times for making false claims: on NHS spending, the rising national debt and the impact of his tax rises and spending cuts on economic growth.

"And only last month the Tories came up with more dodgy figures to claim people are better off, but which totally ignored the impact of things like the rise in VAT and cuts to tax credits.

"In their desperation to paint a rosier picture than the truth, David Cameron and George Osborne are showing just how out of touch they are from reality."

Mr Cameron's official spokesman was challenged over the graph at a regular Westminster media briefing.

Asked whether he conceded that the chart was an attempt to mislead the public, the spokesman replied: "Not at all. The figures and charts set out in that plan are the right ones."